Pulmonary delivery of therapeutic, diagnostic and prophylactic agents provides an attractive alternative to oral, transdermal and parenteral administration. Pulmonary administration can typically be completed without the need for medical intervention (self-administration), the pain often associated with injection therapy is avoided, and the amount of enzymatic and pH mediated degradation of the bioactive agent, frequently encountered with oral therapies, can be significantly reduced. In addition, the lungs provide a large mucosal surface for drug absorption and there is no first-pass liver effect of absorbed drugs. Further, it has been shown that high bioavailability of many molecules, for example, macromolecules, can be achieved via pulmonary delivery or inhalation. Typically, the deep lung, or alveoli, is the primary target of inhaled bioactive agents, particularly for agents requiring systemic delivery.
Pharmaceutical formulations for respiratory delivery are known to be particularly useful for the delivery of proteins and peptides which are difficult to administer by other routes. Proteins and peptides are known to present formulation challenges due to a variety of reasons including their susceptibility to destabilization by physical and chemical factors during the formulation process and during subsequent storage. Thus, pharmaceutical formulations suitable for delivery to the respiratory system having improved physical and chemical stability are desirable.